With the emergence of global travel as a daily occurrence, there are many occasions when an electrically-operated device, such as a battery charger, phone, or computer, is required to draw power from a commercial power source. Such commercial power is typically delivered via a plug mated to a wall receptacle or extension cord receptacle. Unfortunately, there is no single standard for electrical plug/receptacle size, shape, position or number of prongs and there are a wide variety of receptacle configurations in use worldwide. This variety of differing receptacle configurations poses a problem to both manufacturers who sell equivalent products into various parts of the world and to world travelers that need to take electrical devices with them.
Several approaches have be taken to deal with this situation. One approach is to employ a series of distinct adapters which are male on one side and female on the other. When desired, a particular adapter is selected and attached to the electrical primary plug prongs of the device. Then the adapter male end is plugged into the power outlet receptacle. This approach suffers from at least two drawbacks. First, the separate adapter creates an additional item that must be carried by the user and is frequently misplaced. Second, many devices have been designed with a plug or prongs which rotate or fold into the device's casing. For example, some rechargeable flashlights include prongs which can be rotated from a storage position into a deployed position extending out from the body of the flashlight and plugged directly into a wall receptacle or extension cord. For such devices, the adapters are not freely rotatable with the primary prongs, thereby limiting ease of use.
Another approach, disclosed in U.S. Pat. No. 5,713,749 to Wu, utilizes a plurality of separate prong sets having different prong configurations, one of which must be installed into the device for the device to function. Once installed, the prong sets are generally rotatable. However, the Wu approach is complicated to manufacture and requires a significant degree of manual dexterity to install and remove the adapters. Another approach, disclosed in U.S. Pat. No. 4,997,381 to Oh, utilizes a pair of interconnected rotating prong sets which have different prong configurations. The two sets of prongs may be interlocked so as to rotate together. When not desired for use, the prongs may be rotated to a storage position. The approach of Oh is mechanically complicated and difficult to manufacture.
While the approaches of Wu and Oh address one or more of the problems caused by the variety of receptacle configurations, they are not completely satisfactory, if for no other reason than their complexity. Thus, there remains a need for a simple electrical plug assembly designed for use with a plurality of different receptacle configurations which allows for rotating prongs and which is easy to manufacture and use.